Blasting explosive



Patented Aug. 13, 1940 BLASTING EXPLO SHVE Robert W. Cairns, Wilmington, DeL, assignor to Hercules Powder Company, Wilmington, Del., a corporation of Delaware No Drawing.

Application July 8, 1937,

Serial No. 152,668

12 Claims.

This invention relates to blasting explosives, and more particularly to non-gelatinous blasting explosives resistant to water and moisture.

Non-gelatinous blasting explosives, commonly called dynamites, usually consist. of a liquid explosive, e. g. nitroglycerine or mixtures thereof with nitroglycol, ammonium nitrate, sodium nitrate and wood pulp or other carbonaceous material.

A disadvantage of such dynamites is the great hygroscopicity and solubility in water of the inorganic nitrate content thereof. During storage or shipment, such dynamites tend to absorb moisture, and lose sensitiveness to detonation,

because of the increased moisture content. When used in wet boreholes, such dynamites rapidly absorb water and become inert to detonation.

In the past, attempts have been made to overcome this disadvantage by dipping the dynamite cartridge in parafiin wax, or the like, to seal the cartridge against water and moisture, but with only partial success. Attempts have also been made to coat the crystals of inorganic nitrate with waterproofing or moisture-repelling agents,

such as paratfin wax, nitrocellulose, petrolatum, ozokerite, nitrated resin, sodium-, calciumor zinc soaps, sulfurized oils, nitronaphthalenes or nitrotoluenes, sodium silicate, and the like, or with a mixture comprising approximately 15 parts by weight of rosin, 80 parts by weight of paralfin wax and 5 parts by weight of petrolatum,.

but, again, with only partial success.

Coating crystals of inorganic nitrate with nitrocellulose, nitronaphthalenes, or nitrotoluenes is ineiiect'ive for the reason that the nitroglycerin or nitroglycol content of the dynamite dissolves such coatings. Coating inorganic nitrate with the other materials heretofore used has resulted in only partial protection against water and 40 moisture.

I have found that I may prepare coated ammonium nitrate or sodium nitrate or potassium nitrate, which, when used in dynamite, renders said dynamite as water-resistant as semi-gelatin dynamites. This I accomplish by coating the inorganic nitrate with about 0.1% to about 5%, preferably with about 0.5% to about 2% of a solid, recent, natural resin which is compatible with waxy substances or a blend of such resin and waxy substances.

Resins alone are difficult to apply. Their high melting points often require coating temperatures considerably in excess of 100 C., generally considered hazardous on account of the possibility of fire or explosion. Resins may be applied as a coating to inorganic nitrates by the application of a solution of the resin in a volatile solvent followed by evaporation of the solvent, but such application is not very efiective in protecting the inorganic nitrate against water and. 5 moisture. When 1% of rosin in alcohol solution was applied to ammonium nitrate, the product was only 35% good after a water immersion test (as hereinafter described) after 2 hours, compared to 76% good after 2 hours when the rosin 10 was applied to the ammonium nitrate as mplten rosin at 110 C.

The test I employ to determine the resistance to water of coated inorganic nitrate, e. g. ammonium nitrate, and of the dynamite made there- 15 with, comprises packing the material firmly into a 25 cc. Gooch crucible, covering the material with a layer of cheese cloth stretched tightly over the top, immersing the crucible and contents in water at F. in an inverted position to a depth of 2 inches, suspended by wires. After a predetermined time, the crucible and contents are removed and drained, the dry contents separated by a knife from the moistened portion, and the weight of the former determined as percentage of 25 the original content.

I have found that, by mixing the solid, recent, natural resin, compatible with waxy substances, for example, rosin, in the form of a fine powder, with dry, granular ammonium nitrate, then heat- 30 ing the mixture, while stirring, to about 100 C., the resin coats the particles of ammonium nitrate uniformly and completely, forming a product which, by the above-described water test, was 94% good after 2 hours, good after 15 hours. 35 This compares with 35% good after 2 hours when the resin was applied from alcohol solution, and 76% good after 2 hours when the resin was applied in a very hot, molten state.

The resins which I may employ in my process, 40 are solid, recent, natural resins, compatible with common waxes, such as rosin, either wood or gum, dammar, mastic, etc.

Thus, such resins, if properly applied to ammonium nitrate, are excellent waterproofing and 45 moistureproofing agents. However, the relatively high temperature necessary for application is a distinct disadvantage if a molten resin be employed or if a resin solution be employed.

To avoid the necessity of using a solvent for the said resin and to avoid using powdered or molten resin, while at the same time to enable me to produce a uniformly coated and waterproof nitrate, I preferably add various waxy substances to the resin. In so doing I reduce the 100 C. Where, in the specification and claims I use the expression recent, natural resin(s), I mean to include natural resins of recent formation and/or extraction, in distinction to fossil resins. Where in my specification and claims I use the expression Waxy substances I mean to include various waxes such as parafiin, ceresin,

montan, carnauba, candelilla, beeswax, and the like, and synthetic waxes and wax-like substances having melting points below 100 C. and being miscible with the resin in the molten state, and include waxes or wax-like substances, such as higher, solid alcohols, e. g. cetyl, stearyl, lauryl alcohols and the like, higher, solid, organic fatty acids, e. g. palmitic, stearic, myristi'c, etc., or

esters of the last-named acids with monohydric and polyhydric alcohols. These waxy substances may be used in the proportion of 10% to waxy substance and 90% to 50% resin. The melting points of the resultant resin-wax mixtures are such that satisfactory moistureproof and waterproof coatings may be applied to ammonium nitrate at temperatures of about C. to about 100 C. or at temperatures slightly above the melting point of the mixture of resin and waxy substances. Said coating agents need not be applied to the inorganic nitrate in a finely divided condition, butmay be added to the inorganic nitrate in solid pieces or in the molten state, preferably with agitation so as to insure uniform coating of the nitrate with the coating mixture.

As an example of a typical dynamite prepared with a nitrate salt in accordance with my invention, I give the following:

The ammonium nitrate is coated, in accordance with my invention, by stirring with 1% by we1ght of a mixture of parts by weight of rosin and 20 parts by weight of paraffin wax at a temperature of about 100 C. for about 1 hour.

Explosive, A, subjected to the water resistance test herein described, was 69% good after 24 hours. Explosive B was 0% good after 30 minutes exposure to the same test.

What I claim and desire to protect by Letters Patent is:

1. Method of coating a granular inorganic nitrateincluding adding to said nitrate a mixture.

consisting of solid, recent, natural resin, com- 2, 2 1 1,738 melting point of the resin to about 60 C. to about patible with waxy substances, and a waxy substance, heating the mixture to a temperature slightly above the melting point of said mixture, stirring the mixture and cooling the mixture.

2. Method of coating a granular inorganic nitrate including adding to said nitrate a mixture consisting of solid, recent, natural resin, compatible with waxy substances, and a waxy substance, heating the mixture to a temperature between about 60 C. to about 100 C., stirring the mixture, and cooling the mixture.

3. Method of coating granular ammonium nitrate including adding to granular ammonium nitrate a mixture consisting of rosin and paraflin wax, heating the mixture to about 100 C., stirring the mixture, and cooling the mixture.

4. Method of coating granular ammonium nitrate including adding to granular ammonium nitrate a mixture consisting of to 50 parts by weight of rosin and 10 to 50 parts by weight of parraflin wax, heating the mixture to about C., and cooling the mixture.

5. A granular inorganic nitrate coated with a substance consisting of a mixture of a solid, recent resin compatible with waxy substances and a waxy substance.

6. Granular ammonium nitrate coated with a substance consisting of a mixture of a solid, recent resin compatible with waxy substances and a waxy substance.

7. Granular ammonium nitrate coated with a substance consisting of a mixture of rosin and paraflin.

8. Granular ammonium nitrate coated with a substance consisting of a mixture consisting of rosin 90 to 50 parts by weight and paraflin wax 10 to 50 parts by weight.

9. An explosive including granular ammonium nitrate coated with a substance consisting of a mixture of rosin and parafiin wax.

10. Method of coating a granular inorganic nitrate including adding to said nitrate a mixture consisting of 90 to 50 parts by weight of solid, recent, natural resin compatible with waxy substances, and 10 to 50 parts by weight of a waxy substance, heating the mixture to a temperature between about 60 C. to about 100 C. and cooling the mixture.

11. Method of coating granular ammonium nitrate including adding to granular ammonium nitrate a mixture consisting of 90 to 50 parts by weight of rosin and 10 to 50 parts by weight of parraifin wax, heating the mixture to a temperature between about 60 C. to about 100 C., and cooling the mixture.

12. An explosive including granular inorganic nitrate coated with a substance consisting of a mixture of rosin and paraflin wax.

ROBERT W. CAIRNS. 

